Phosphine functionalization of GaAs(111)A surfaces

Phosphorus-functionalized GaAs surfaces have been prepared by exposure of Cl-terminated GaAs(111) A surfaces to triethylphosphine (PEt₃) or trichlorophosphine (PCl₃), or by the direct functionalization of the native-oxide terminated GaAs(111) A surface with PCl₃. The presence of phosphorus on each functionalized surface was confirmed by X-ray photoelectron spectroscopy. High-resolution, soft X-ray photoelectron spectroscopy was used to evaluate the As and Ga 3d regions of such surfaces. On PEt₃ treated surfaces, the Ga 3d spectra exhibited a bulk Ga peak as well as peaks that were shifted to 0.35, 0.92 and 1.86 eV higher binding energy. These peaks were assigned to residual Cl-terminated Ga surface sites, surficial Ga₂O and surficial Ga₂O₃, respectively. For PCl₃-treated surfaces, the Ga 3d spectra displayed peaks ascribable to bulk Ga(As), Ga₂O, and Ga₂O₃, as well as a peak shifted 0.30 eV to higher binding energy relative to the bulk signal. A peak corresponding to Ga(OH)₃, observed on the Cl-terminated surface, was absent from all of the phosphine-functionalized surfaces. After reaction of the Cl-terminated GaAs(111)A surface with PCl₃ or PEt₃, the As 3d spectral region was free of As oxides and As⁰. Although native oxide-terminated GaAs surfaces were free of As oxides after reaction with PCl₃, such surfaces contained detectable amounts of As⁰. Photoluminescence measurements indicted that phosphine-functionalized surfaces prepared from Cl-terminated GaAs(111)A surfaces had better electrical properties than the native-oxide capped GaAs(111)A surface, while the native-oxide covered surface treated with PCl₃ showed no enhancement in PL intensity.